1. Field of the Invention
This invention relates to an electrophotographic photosensitive material, and more particularly, to an improvement in and relating to an organic polymeric photoconductive material whose mechanical strength and adhesion to an electrically conductive substrate are increased without a deleterious effect on its electrophotographic properties.
2. Description of the Prior Art
It is known that organic polymeric photoconductors such as poly-N-vinylcarbazole (to be sometimes abbreviated as PVK hereinafter) are film-forming by themselves, and a material comprising an electrically conductive substrate and coated thereon, a photoconductive layer composed of a charge transfer complex of such an organic polymeric photoconductor with an electron accepting substance (Lewis acid), for example, is used as a photosensitive material for electrophotography.
The organic polymeric photoconductors such as PVK have the defect that they are brittle in nature, and photosensitive materials prepared therefrom undergo easy peeling of the photoconductive layer from the substrate, and have low resistance to abrasion or impact. In order to remedy this defect, various attempts have been made to improve the adhesion of PVK to the substrate and the mechanical properties of a film of PVK itself by incorporating an organic high-molecular-weight polymer having no photoconductivity as a reinforcing agent in PVK. Various thermoplastic polyesters or polycarbonates are known as such a polymeric reinforcing agent, and for example, Japanese Laid-Open Patent Publication No. 57440/1975 discloses that a thermoplastic aromatic polyester derived from bisphenol A and a benzenedicarboxylic acid is used as a reinforcing agent for PVK.
This thermoplastic aromatic polyester is generally satisfactory for the purpose of increasing the tensile strength of the photoconductive layer without much reducing the sensitivity of PVK, but the adhesion of the resulting photoconductive layer to a substrate and its surface hardness are still low. Hence, this polyester does not prove to be entirely satisfactory in regard to abrasion resistance.